1. Field of the Invention
The present invention relates to a managing system of permitting reproduction of program information when the program information to be reproduced is recorded in an optical disc such as a CD (Compact Disc) or a DVD (Digital Video Disc or Digital Versatile Disc), particularly, and relates to improvements in a cipher key producing method, a cipher key writing method, a cipher key reproduction apparatus, an information reproduction method, an information reproduction permitting method, and a reproduction apparatus of optical disc so as to protect an optical disc from illegal utilization thereof and illegal duplication or copy therefrom.
2. Description of the Related Art
In an optical disc package media such as a CD, all program information contained in an optical disc is disclosed to an owner of the disc, that is, an owner of an optical disc can utilize all program information contained in the disc when the owner possesses the disc. As shown in FIG. 1, a software supplier (software house) 28 supplies an optical disc 11 as indicated by an arrow 15 and collects a fee for the sold optical disc 11 by indicated by an arrow 16. A price of the optical disc 11 is fixed for total program information which is contained in the disc 11. A consumer pays a fixed price for the optical disc 11 in the current distribution system 10, that is, a consumer pays a fixed price for a "possession" of the program information which is contained in the optical disc 11.
Generally, a price of the optical disc 11 is determined primarily for quality and quantity of program information contained in the disc 11, since the optical disc 11 without its program content can be manufactured at an extremely low cost. In a distribution system 10, a consumer is obliged to pay a total cost of the program information contained in the optical disc 11 although not all of such program information are wanted by the consumer. In other words, manufacturers of optical discs are obliged to manufacture wide variety of optical discs in their contents to meet a wide variety of demands by consumers. This causes a price boost of each of such discs. On the other hand, as consumers prefer to purchase optical discs at lower prices, the above situation invites illegally duplicated optical discs sold at very low prices into the market. The above mentioned distribution system 10 is not only unfavorable to the consumers but also increases cost and complexity of distribution for manufacturers and software houses.
In contrast with the above mentioned distribution system 10, a "super distribution system" 20 is known. The "super distribution system" 20 is a system of paying for a "utilization" of the program information not for a "possession" of program information. According to the "super distribution system" 20, a consumer just pays for a utilized program information. The unfavorable deal in the above mentioned distribution system 10 of paying for a "possession" of program information is dissolved by the "super distribution system" 20 and it is supposed to be a more rational system. In the "super distribution system" 20, a utilization state of program information and information of limitation of the utilization are transmitted to a managing system through a communication network.
As shown in FIG. 1, an optical disc 21 is supplied at a low price by a software house 28 a shown by an arrow 25, wherein program information recorded in the optical disc 21 is coded so as to comply with the "super distribution system". An optical disc player 22 which reproduces program information (software) recorded in the optical disc 21 is equipped with a connector 24 for an IC card and a communication port 23 for a telephone line. Data of credited amount for reproduction is prestored in the IC card and the data is renewed at each time when reproducing the program information so as to deduct the credited amount. The communication port 23 is connected to a host computer of a software house 28 through a telephone line wherein reproduction fees of optical discs are collected as indicated by an arrow 26 and a revised credited amount responsive to the reproduction is newly set as indicated by an arrow 27. A software house 28 includes dealers such as retailers and credit card issuing companies.
FIG. 2 shows an example of a "super distribution system". The example is applied to game software. For example, an optical disc 900 recorded with a game software is supplied together with an extra software of a magazine 902 to game players. In other words, a user of the game software obtains the optical disc 900 by purchasing the magazine 902 as indicated by an arrow 911.
An inherent ID (identification) which identifies individual optical discs is recorded on the optical disc 900. To record the inherent ID on prerecorded optical discs individually, the U.S. Pat. No. 5,400,319 discloses a method of recording information of less recording density than the recording density of main information (essential information of an optical disc) on an information recording surface of an optical disc after the optical disc is manufactured. Recording information in a recording area of low packing density is realized by permanently deforming a reflective membrane of a substrate of the optical disc by irradiating a strong laser beam. A typical linear recording density of such a low density information is from 1/10 to 1/1000 of the recording density of main information, preferably an extent of from 1/40 to 1/400.
A personal computer (or player) 904 which reproduces the optical disc 900 is provided with a connector and a communication port, whereto an IC card 906 and a modem 908 are connected. Data of credited amount for reproducing a game software is prestored in the IC card 906 and the data is renewed at the time upon reproducing the game software so as to deduct the credited amount. The modem 908 is connected to a management computer 910 of a supplier (software house) of the game software through a communication line. In the management computer 910, credited amount is set and reproduction fees are collected.
A user loads the optical disc 900 on the personal computer 904. The personal computer 904 transmits the following information (1) through (4) to the management computer 910 as indicated by an arrow 912: (1) an ID of the optical disc 900 and a drive number of a drive unit which reproduces the optical disc 900, (2) an ID of the game software to be reproduced, (3) an ID of the personal computer 904 as a reproduction device, and (4) an ID of the IC card 906. In the management computer 910, a cipher key (or cipher number) is produced by combining the received information and then the cipher key is transmitted to the personal computer 904 as indicated by an arrow 913. Simplest example is explained as follows with assumption of that the ID of the optical disc is "123", the drive number is "122", the ID (title key) of the game software to be reproduced is "666", and the cipher key is "421". The management computer 910 adds "123" of the optical disc ID, "122" of the drive number both entered by the user, and "421" of the cipher key together. A sum becomes "666" (123+122+421=666). The number "666" is the title key to be reproduced, then the personal computer 904 reproduces the game software of the title key "666".
Accordingly, before reproducing an optical disc, a user contacts first with a software house to obtain a cipher key which is necessary to utilize program information to be reproduced. Then the user can reproduce the program information by utilizing the cipher key. One software which is related to the cipher key out of several game softwares contained in one optical disc 900 is reproduced. A cost for utilizing the program information is deducted from an amount of money which is prestored in the IC card 906. The user can enjoy a game software within the credited amount of the IC card 906.
Moreover, in the "super distribution system", program information recorded in an optical disc can not be utilized without a cipher key although an optical disc is available, therefore optical discs are prevented from illegal duplication. Since a cipher key is produced in conjunction with the inherent ID of an optical disc, a cipher key can be prepared for individual optical discs, that is, one cipher key can be utilized for just one optical disc. Therefore, it is impossible to utilize one cipher key for various optical discs or for several users.
According to the above mentioned "super distribution system", different cipher keys are prepared for individual optical discs, therefore a user is obliged to manage the cipher keys. Especially, in the case of possessing many optical discs, a user is obliged to enter a different cipher key for a different optical disc whenever reproducing an optical disc. The "super distribution system" is very convenient for a software house so that security for illegal utilization and illegal duplication is enhanced. On the other hand, a cipher key varies by program information, so that managing various cipher keys is rather difficult for a user.